1. Field of the Invention
The present invention relates to a method and an apparatus for inspecting an edge exposure area of a wafer, more particularly to a method and an apparatus for measuring a width between an edge of the wafer and an edge of a photoresist layer formed on the wafer.
2. Description of the Related Art
Generally, semiconductor devices are manufactured by performing a fabrication process for forming an electric circuit on a silicon wafer which is used as a semiconductor substrate, an electrical die sorting (EDS) process for inspecting electrical characteristics of the semiconductor devices, and a package process for sealing and individualizing the semiconductor devices with epoxy resin.
The fabrication process includes a deposition process for forming a film on the semiconductor substrate, a chemical mechanical polishing (CMP) process for planarizing the film, a photolithography process for forming a photoresist pattern on the film, an etching process for patterning the film using the photoresist pattern in order to give electrical properties, an ion implantation process for implanting ions into predetermined portions of the semiconductor substrate, a cleaning process for removing impurities on the semiconductor substrate, and an inspection process for detecting a defect of the semiconductor substrate having the film and the pattern.
The photoresist pattern formed by the photolithography process is inspected using a microscopic inspection process before performing the etching process. In the microscope inspection process, a microscope is employed to inspect any defects of the photoresist pattern and to inspect an edge exposure area adjacent to the edge portion of the semiconductor substrate.
The edge portion of the photoresist layer formed on the semiconductor substrate is removed during an edge exposure process, e.g., using an ultraviolet ray and a developing solution. The edge exposure area indicates a ring shaped area between the edge of the wafer and the edge of the photoresist layer.
The process for inspecting the edge exposure area using the microscope is performed in order to inspect the width of the edge exposure area. However, results of the process for inspecting the edge exposure area are highly dependent on the skill of a person performing the inspection, reducing the reliability and reproducibility of the results. Further, the wafer may be contaminated when handled by a human.
In order to solve the above-mentioned problems, an apparatus having an imaging component for inspecting the edge exposure area has been developed. The imaging component can obtain the image of the edge portion of the wafer, analyze the image, and calculate the width of the edge exposure area. Because the image is obtained by the light scattered from the edge portion of the wafer, it is difficult to detect the position of the edge of the photoresist layer. Accordingly, when the edge exposure area where various films and patterns are formed is inspected using a conventional apparatus, the process for inspecting the edge exposure area may still not be sufficiently reliable.